Femtosecond time resolved studies have elucidated the mechanism for the reaction CH4 + O(1D) ® CH3 + OH. Ozone in the CH4·O3 van der Waals cluster with photolyzed by 266 nm laser pulses, producing O(1D), and the appearance of OH (v=0,1; J) was determined by OH A ¬ X laser induced fluorescence as a function of pump/probe delay time. The appearance of OH A ¬ OH X was measured at six different probe wavelength regions ranging from 307.3 nm to 316.5 nm where each probe wavelength measures a different distribution of OH vibrational (v) and rotational (J) states. At each probe wavelength the reaction exhibits both a slow and fast formation time. The data supports a simple model in which OH is produced by two mechanisms: a slow mechanism where OH is formed from a CH3OH* intermediate in which the available energy randomizes and dissociates with a rate expected from RRKM theory; a fast mechanism where OH is formed from a CH3OH* intermediate which dissociates prior to energy randomization.